Rhubarb Upside-Down Cake - cooking recipe

Ingredients

4 Tbsp. unsalted butter
3/4 c. brown sugar
3 c. diced rhubarb (1/4-inch dice)
2 Tbsp. granulated sugar
1 c. granulated sugar
1/2 c. unsalted butter, softened
2 eggs, separated
1 tsp. vanilla extract
1 1/2 c. all-purpose flour
1/2 tsp. salt
2 tsp. baking powder
1/2 c. milk
1/4 tsp. cream of tartar

Preparation

Preheat oven to 350\u00b0.
Generously butter a 9-inch iron skillet.
Melt 4 tablespoons unsalted butter over low heat.
Stir in the brown sugar.
Pour into skillet and distribute evenly across the bottom of the pan.
Place rhubarb in pan and sprinkle with 2 tablespoons granulated sugar.
Set aside.